Many investigators and clinicians feel that glucose is a necessary and essential component in cardioplegia solutions. There is a large body of evidence which indicates that the presence of glucose during anoxia is advantageous and an equally impressive body of evidence which shows that if glucose is present during total ischemia it is detrimental. Paradoxically, clinical evidence suggests that glucose as a component in cardioplegia is, at least, not deleterious. Whether or not it is protective under clinical conditions has not been well established. It has been argued that this conflict may be explained by the "washout" of lactic acid during the elective ischemia of surgery by intermittently reperfused cardioplegia solution and/or non-coronary collateral flow. The objective of the investigation proposed in this application is to evaluate the effectiveness of glucose as a cardioplegic agent when it is added to a cardioplegia solution designed to initiate myocardial arrest, and is subsequently reinfused intermittently during the ischemic period. Our hypothesis is that multiple infusions of a glucose containing cardioplegia solution during myocardial ischemia at 28 degrees C will be detrimental to tissue protection. To prove our hypothesis we propose to use an isolated rabbit heart model of myocardial ischemia to compare myocardial contractility (papillary muscle) following eighty minutes of myocardial ischemia when a glucose containing cardioplegia solution is reperfused intermittently at 20 minute intervals throughout the ischemia, with the contractility measured after an identical ischemic arrest in which the same cardioplegia is (intermittently) reperfused but the glucose is not included. Myocardial contractility in both instances will be correlate with myocardial lactic acid concentration. We also propose to repeat these measurements for eight minute ischemic periods at 15 degrees C and 20 degrees C to determine if hypothermia alters the contractility following the ischemia, and the expected deleterious effects of glucose.